Helical gear pump with adjustable stator compression



June 18, 1957 J, D BOURKE 2,796,029

HELICAL GEAR PUMP WITH ADJUSTABLE STATOR COMPRESSION v Filed Aug. 15,1955 Y @@Yzaw ATTORNEYS.

United States atent Patented June 18, 1957 HELICAL GEAR PUMP WITHADJUSTABLE STATOR COR/[PRESSION John David Bourke, Springfield, Ohio,assigner to Robbins & Myers, Inc., Springfield, Ohio, a corporation ofOhio Application August 15, 1955, Serial No. 528,226

6 Claims. (Cl. 103--117) This invention relates to helical gear pumps ofthe type invented by R. l. L. Moineau wherein a helically externallythreaded rotor coacts with an internally helically threaded stator, saidstator having one more thread than said rotor. Pumps of this generallytype are now conventional built with a metallic rotor which is rigid anda stator which is of a exible or resilient material such as rubber.Pumps of this type are advantageous particularly in handling abrasivematerials but it has been found that the abrasive materials produce wearand that this wear is usually greatest toward the discharge end of thepump.

With these considerations in mind, it is an object of the presentinvention to provide means for adjusting the stator compression in ahelical gear pump and to provide such means which may be adjusted fromthe exterior of the pump so that it is unnecessary to take the pumpapart to make the adjustment.

against the stator. In some types of pumps, it is necessary to providesealing means for the screw and in others sealing means may be omitted.

Referring in greater detail to the drawing, a pump is indicatedgenerally at 10 having a casing 11 and ports 12 and 13. The pump itselfwill not be described in detail except insofar as is necessary for anunderstanding of the present invention. The pump comprises a rotor 14which is of rigid material and a stator 15 which is of rubber orrubber-like material. The rotor 14 is connected to a drive shaft 16 bymeans of a universal joint generally indicated at 17.

ln the particular embodiment of Figures l, 2 and 3, the stator isprovided with the end flanges 18, one at each end, and with the lateralextensions 19 by means of which it is non-rotatably held in the casing10. As best seen in Figure 3, the casing is in two parts, the lowerportion being designated 11a and the upper portion being designated 11b.The two parts are held together by bolts 20 passing through flanges inthe casing portions 11a and 11b and when the casing portions 11a and 11bare secured together, the extensions 19 are clamped in position.

In the embodiment of Figures l to 3, it will be observed that theinterior of the casing portions 11a and 11b is cylindrical but that theradius inside the portion 11b is larger than that inside the portion11a, so that room is left between the stator 15 and the casing portion11b for a rigid casing liner element 21. The liner element 21 and thecasing portion 11a snugly embrace the cylindrical stator 15.

Substantially centrally of the casing portion 11b I l provide a boss 22which may be reinforced by the webs 23 It is another object of theinvention to provide adjustl ing means which will be self-aligning sothat the adjustment may compensate for increased wear toward one end ofthe pump or the other.

It is still another object of the invention to make it possible toincrease the capacity of such a pump at higher pressures or in otherwords to reduce the degree to which the capacity drops off as thepressure is increased. Yet another object of the invention is to providemeans whereby the maximum eiiiciency of the pump may be made to occur athigher pressures than has been possible heretofore.

These and other objects of the invention which will be pointed out inmore detail hereinafter or which will be apparent to one skilled in theart upon reading these specifications, I accomplish by that constructionand arrangement of parts of which I shall now disclose exemplaryembodiments.

Reference is made to the drawings forming a part hereof and in which:

Figure l is a plan View of a typical pump to which the invention may beapplied.

Figure 2 is an elevational View of the same with parts in section.

Figure 3 is a cross-sectional view taken on the line 3-3 of Figure 2.

Figure 4 is an elevational view with parts in section of a modified typeof pump, and

Figure 5 is a cross-sectional view taken on the line 5 5 of Figure 4.

Briefly, in the practice of the invention, I provide between theflexible or resilient stator and the pump casing surrounding the statora part-cylindrical rigid casing liner extending substantially the fulllength of the stator. Substantially centrally thereof I provide a bossin the casing having a threaded hole to accept a threaded screw. Thethreaded screw at its outer end is provided with means for attachment ofa wrench or the like and means are provided for locking the screw in adesired adjusted position. The screw bears against the casing liner andforces it and 24. This boss has a threaded hole to accept the screw 25which may be squared at its outer end as at 26. It will now be clearthat as the screw 26 is tightened it causes the liner member 21 to bearagainst the stator 15 and thus to put pressure on the stator. Becausethe screw 25 operates substantially centrally of the member 21, themember 21 is in etfect self-aligning and the member 21 can pivot inrelation to the screw.

To x the screw in a desired adjusted position, I preferably slot theboss 22 as at 27 and the screw itself is drilled to accept a cotter pin28. In the figures, I have shown two slots 27 normal to each other sothat the screw may be xed at any desired quarter turn position. It willbe clear that a single slot could be used or that more than two slotscould be used if a liner adjustment is desired.

ln the pump of Figures l to 3, because the stator 15 is sealed inrelation to the casing members 11a and 11b by virtue of the flanges 18and the lateral extensions 19, no sealing means need be provided for thescrew 25.

In the embodiment of Figures 4 and 5, wherein the pump is of the samegeneral type, there is a flange 18a at only one end of the stator 15a,and for this reason it is necessary to provide sealing means for thescrew. As best seen in Figure 5, an O-ring is provided at 30 to seal theentrance of the screw 25a. The screw is slightly modified in that it hasa portion 2517 free of threads to cooperate with the O-ring 30.

In the embodiment of Figures 4 and 5, it will also be observed that theinterior of the casing llc` is cylindrical and therefore a supplementarylining member 21a is provided to cooperate with the liner 21 in snuglyembracing the stator 15a. The casing in the pump of Figures 4 and 5 isin one piece as compared with that of Figures l to 3 which is in twopieces, and the stator of course does not have the lateral extensions19. The function of the adjusting screw and the manner of locating itare the same as described above.

I have found that taking a typical pump with no adjustment of the screwhaving a capacity at zero pressure of about one hundred seventeengallons per minute, that capacity drops to one hundred four gallons perminute at one hundred pounds per square inch and has dropped toeighty-six gallons per minute at one hundred fty pounds per square inchand to fifty-six gallons per minute at two hundred pounds .per squareinch. After putting one full turn on the screw, the capacity at zeropressure was one hundred twelve gallons per minute, at one hundredpounds per square inch it was one hundred six gallons per minute, at onehundred fifty pounds per square inch it was ninety-six gallons perminute, and at two hundred pounds it was seventy-two gallons per minute,With two full turns on the screw the capacity was one hundred fourgallons per minute at zero pressure and remained at one hundred fourgallons per minute up to onehundred pounds per square inch, had droppedonly to one hundred gallons per minute at one hundred fifty pounds persquare inch and to ninety-three gallons per minute at two hundred poundsper square inch. Thus, while the capacity was not changed greatly atabout one hundred pounds per square inch by adding: one or two turns tothe screw, the capacity at two hundred pounds per square inch was verymuch greater with two turns of the screw than with only one turn or noturns.

Adjustment of the screw to increase compression on the stator does notappreciably atfect the maximum eiciency of the pump but it shifts thepoint of maximum efliciency to different pressures Thus, for example,the same pump with no turns on the screw had a maximum eiciency of about70% at eightyve pounds per square inch. When one turn was put on thescrew, the point of maximum efficiency was shifted to about one hundredten pounds per square inch and when two turns were put on the screw, thepoint of maximum eiciency was shifted to about one hundred forty-fivepounds per square inch.

An advantage of the construction disclosed herein, therefore, is that astandard pump may be adjusted to operate at maximum efficiency at thespeciic pressure encountered.

It will be clear that various modifications may be made withoutdeparting from the spirit of the invention and I therefore do not intendto limit myself otherwise than as set forth in the claims hereinafter.

Having now fully described my invention, what I claim as new and desireto secure by Letters Patent is:

1. In a helical gear pump wherein an externally helically threaded rigidrotor pumpingly coacts with an internally helically threaded resilientstator, the said stator being retained within a rigid easing element; apartcylindrical rigid casing liner element interposed between saidstator and casing element, said stator being snugly embraced by saidcasing element and liner, a boss in said casing element having athreaded hole, and a screw in said hole, the inner end of said screwbearing against said liner, whereby by adjustment of said screw thepressure of said stator against said rotor may be adjusted from theoutside.

2, A pump according to claim 1, wherein said boss has at least onediametral slot and said screw has a diametral hole, whereby a cotter pinmay be passed through said hole in said screw when in alignment withsaid slot to x the position of said screw.

3, A pump according to claim l, wherein two less-thanhalf-cylindricalliner relements are interposed between the said stator and casingelement, said screw acting upon one of said liner elements.

4. A pump according to claim 1, wherein said casing clement isconstituted in two halves, one half having a larger internal diameterthan the other, said liner element lying in said one half and having aninternal diameter equal to that of the other half.

5. A pump according to claim 1, wherein means are provided to seal thesaid screw with respect to said hole.

6. A pump according to claim 5, wherein said seal means includes anO-ring, and said screw has a smooth shank contacting said O-ring.

References Cited in the file of this patent UNITED STATES PATENTS 81,778Hardy Sept. l, 1868 89,268 Andrew Apr. 27, 1869 171,651 Crocker Jan, 4,1876 2,028,407 Moineau Jan. 21, 1936 2,483,370 Moineau Sept. 27, 19492,504,230 Smith Apr. 18, 1950 .2,697,987 Barclay Dec, 28, 1954

